Why 300% and 126% exactly? Am I missing something.My best is Lucario. He's quick on foot, and has his attack power rises the more damage he takes. Not only that, but Extremespeed prevents a lot of attacks from happening. Aura sphere is also useful when you're up to 300% or 126%. It usually is a one-hit KO on high damage opponents.
My absolute worst is.... I have no clue.